Error 500 with Google AppEngine, and class java.net -

i have problem gae. have application http://www.similarityface.appspot.com/query. trying through program in java communicate application perform query, via post method. problem generating 500 error. code below, me telling i'm doing wrong.

public class vetores_facebook {    public static void main(string[] args) throws unsupportedencodingexception, ioexception {         final string server = "https://www.similarityface.appspot.com/query";         url url = null;         try {             url = new url(server);      } catch (malformedurlexception ex) {         logger.getlogger(vetores_facebook.class.getname()).log(level.severe, null, ex);     }      httpurlconnection urlconn = null;     try {         // url connection channel.         urlconn = (httpurlconnection) url.openconnection();      } catch (ioexception ex) {         logger.getlogger(vetores_facebook.class.getname()).log(level.severe, null, ex);     }       urlconn.setdooutput (true);      // no caching, want real thing.     urlconn.setusecaches (false);      try {              urlconn.setrequestmethod("post");     } catch (protocolexception ex) {         logger.getlogger(vetores_facebook.class.getname()).log(level.severe, null, ex);     }      try {          urlconn.connect();     } catch (ioexception ex) {         logger.getlogger(vetores_facebook.class.getname()).log(level.severe, null, ex);     }      string message = urlencoder.encode("get_object(\"me\", metadata=1)", "utf-8");     try (outputstreamwriter writer = new outputstreamwriter(urlconn.getoutputstream())) {         writer.write(message);         writer.close();      }         if (urlconn.getresponsecode() == httpurlconnection.http_ok) {          system.out.println("ok");         }      else{             int x = urlconn.getresponsecode();             system.out.println("error "+x);       }  } } 

try {      urlconn.connect(); } catch (ioexception ex) {     logger.getlogger(vetores_facebook.class.getname()).log(level.severe, null, ex); }  string message = urlencoder.encode("get_object(\"me\", metadata=1)", "utf-8"); try (outputstreamwriter writer = new outputstreamwriter(urlconn.getoutputstream())) {     writer.write(message);     writer.close();  } 

the problem calling urlconn.connect(); seems flush output buffers may have , prepares connection input stream. trying write open output stream after cause exception.

use example given here correct way this: https://developers.google.com/appengine/docs/java/urlfetch/usingjavanet#using_httpurlconnection